1. Field of the Invention
The present invention relates to an electron beam apparatus wherein a first substrate, which includes an electron-emitting device, is positioned opposite a second substrate, for projecting an electron discharged by the electron-emitting device, and wherein a spacer is provided between the first substrate and the second substrate.
2. Related Background Art
Since a plane type display device is thin and light, it has been focused on as a replacement for a Braun tube display device. Especially for a display device that employs together an electron-emitting device and a phosphor that emits light when irradiated by an electron beam, a characteristic superior to that of conventional display devices of other types is expected. Compared with, for example, the liquid crystal display device that has been popular, a plane type display device is superior because a backlight is not required, it is a self-emission type and has a large viewing field angle.
Conventionally, there are two well known types of electron-emitting devices: a heat-cathode device and a cold-cathode device. As a cold-cathode device, for example, a surface conduction electron-emitting device, a field-emitting device (hereinafter referred to as a FE type), and a metal/insulating layer/metal emission device (hereinafter referred to as an MIM type) are known.
As a surface conduction electron-emitting device, for example, a device described by M. I. Elinson, Radio Eng. Electron Phys., 10 1290 (1965), and another device that will be described later are known.
The surface conduction electron-emitting device employs a phenomenon that permits electron emissions when a current flows in parallel to the surface of a small thin film that is formed on a substrate. As a surface conduction electron-emitting device, not only the device proposed by Elinson, which employs an SnO2 thin film, but also a device that uses an Au thin film (xe2x80x9cThin Solid Filmsxe2x80x9d, G. Dittmer, 9, 317(1972)), a device that uses In2O3/SnO2 (xe2x80x9cIEEE Trans. ED Conf.xe2x80x9d, M. Hartwell and C. G. Fonstad, 519 (1975)), and a device that uses a carbon thin film (xe2x80x9cVacuumxe2x80x9d, Hisashi Araki et al., vol. 26, No. 1, 22 (1983)) have been reported.
As a specific example of the device arrangements for these surface conduction electron-emitting devices, FIG. 30 is a plan view of a device proposed by M. Hartwell, et al. In FIG. 30, an electroconductive thin film 3004 of metal oxide is formed in a flat H shape on a substrate 3001 by sputtering. An electron-emitting region 3005 is formed by performing, for the electroconductive thin film 3004, an operation called energization forming, which will be described later. In FIG. 30, an interval L is set to 0.5 to 1 mm and a width W is set to 0.1 mm. For convenience sake, the electron-emitting region 3005 is represented as having the rectangular shape shown in the center of the electroconductive thin film 3004; however, this shape is merely a specific example, and the actual position and shape of the electron-emitting region are not precisely shown.
Since when compared with a hot-cathode device a cold-cathode device emits electrons at a low temperature, it does not require a heater. Therefore, a cold cathode device is arranged more simply than is a hot-cathode device, and a delicate device can be fabricated. Further, even when multiple devices are arranged at a high density on a substrate, a problem such as the heat welding of the substrate seldom occurs. In addition, while the response speed of a hot-cathode device is low because to operate it must be heated by a heater, the response speed of the cold-cathode device is high.
Therefore, the study of the employment of a cold-cathode device has become very popular.
Since of the cold-cathode devices, the surface electroconductive electron-emitting device in particular is structured simply and is easily fabricated, and multiple devices can be formed in a across a wide area, methods for arranging and driving multiple devices are therefore studied, as is disclosed in Japanese Unexamined Patent Publication No. 64-31332, submitted by the present applicant.
Further, an image forming apparatus, such as an image display apparatus or an image recording apparatus, and an electron beam apparatus, such as a charge beam source, are studied for application with a surface conduction electron-emitting device.
An image display apparatus that employs both a surface conduction electron-emitting device and a phosphor that emits light when an electron collision occurs is: especially studied as an example application, as is disclosed by the present applicant in U.S. Pat. No. 5,066,883 and Japanese Patent Publications No. 2-257551 and No. 4-28137.
FIG. 31 is a perspective view of an example display panel that serves as a flat panel image display, with one part of the panel cut away in order to show the internal structure. In FIG. 31, reference numeral 3115 denotes a rear plate; 3116, a side wall; and 3117, a face plate. The rear plate 3115, the side wall 3116 and the face plate 3117 form an envelope (an airtight container) to maintain a vacuum inside the display panel.
A substrate 3111 is fixed to the rear plate 3115, and cold-cathode devices 3112 are arranged in an Nxc3x97M matrix shape on the substrate 3111 (N and M are positive integers of two or greater, and are determined as needed in accordance with the target number of display pixels). As is shown in FIG. 31, the Nxc3x97M cold-cathode devices 3112 are laid out along M lines of row-directional wiring 3113 and N lines of column-directional wiring 3114. The portion constituted by the substrate 3111, the cold-cathode devices 3112, the row-directional wiring 3113 and the column-directional wiring 3114 is called a multi-electron beam source. At least at portions where the lines of row-directional wiring 3113 and the lines of column-directional wiring 3114 intersect, insulating layers (not shown) are formed between lines of wiring, and electric insulation is maintained.
A phosphor film 3118, which is prepared using phosphors, is deposited on the lower surface of the face plate 3117, and phosphors (not shown) in three primary colors, red (R), green (G) and blue (B), are painted on it. Further, a black member (not shown) is located between the individual phosphors that constitute the phosphor film 3118, and a metal backing 3119 composed of Al, etc., is formed on the surface of the phosphor film 3118, near the rear plate 3115.
Dx1 to DxM, Dy1 to DyN and Hv are airtight electric terminals used to electrically connect the display panel to an electric circuit (not shown). Dx1 to DxM are electrically connected to the lines of row-directional wiring 3113 of the multi-electron beam source; Dy1 to DyM, are electrically connected to the lines of column-directional wiring 3114 of the multi-electron beam source; and Hv is electrically connected to the metal back 3119.
A vacuum of approximately 1.3xc3x9710-3 [Pa] (10-6 [Torr]) is maintained inside the airtight container, and as the display area of the image display apparatus is increased, means is required to prevent the deformation or the destruction of the rear plate 3115 and the face plate 3117, which could occur due to the pressure difference between the inside and the outside of the airtight container. A method according to which the rear plate 3115 and the face plate 3116 are thickened not only results in an increase in the weight of the image display apparatus, but also in the distortion of an image or parallax when viewed obliquely, whereas structure support members (called spacers or ribs) 3120 formed of a comparatively thin glass plate, as shown in FIG. 31, provide support and resist the atmospheric pressure. With this arrangement, normally an interval of a submilimeter or several millimeters is maintained between the substrate 3111, on which the multi-beam electron source is mounted, and the face plate 3117, on which the phosphor film 3118 is deposited. As is described above, this contributes to the maintenance of a high vacuum inside the airtight container.
In an image display apparatus that employs the thus described display panel, when a voltage is applied to the cold-cathode devices 3112 via the external container terminals Dx1 to DxM and Dy1 to DyN, electrons are emitted by the cold-cathode devices 3112. At the same time, a high voltage of several hundred Vs to several kVs is applied to the metal back 3119, via the external container terminal Hv, to accelerate the emitted electrons so that they collide with the internal wall of the face plate 3117; As a result, the individual color phosphors of the phosphor film 3118 are excited and emit light, and an image is displayed.
For the following reason, the spacers 3120 positioned inside the display panel are required to have high insulation and high electrification suppression capabilities so that they can resist the high voltages that are is applied to the face plate 3117 and the rear plate 3115.
First, when a part of the electrons emitted by the cold-cathode devices 3112 near a spacer 3120 strike the spacer 3120, or when the electrons of that part which reach and are reflected by the face plate 3117 strike the spacer 3120, a secondary electron emission occurs, and this may result in the electrification of the spacer 3120. In accordance with information obtained by the present applicant, in most cases a positive charge is induced on the surface of a spacer 3120. Then, since the spacer 3120 is charged, the trajectories of electrons emitted by the cold-cathode device 3112 are bent, and the electrons arrive at positions on the phosphor on the phase plate 3117 that differ from the normal position. As a result, near the spacer a displayed image is distorted.
Second, since a high voltage of several hundred Vs or more (i.e., a high electric field of 1 KV/mm or greater) is applied between the multi-electron beam source and the face plate 3117 in order to accelerate electrons that are emitted by the cold-cathode devices 3112, a creeping discharge can occur on the surface of a spacer 3120. Especially when a spacer 3120 is charged as described above, a discharge may be induced.
To resolve this problem, one proposal provides for the supply of a micro-current to a spacer to remove a charge (Japanese Unexamined Patent Publications No. 57-118355 and No. 61-124031). Thus, according to this proposal a thin film having high resistance is formed, as a charge prevention film, on the surface of an insulating spacer to supply a micro-current to the surface of the spacer. The charge prevention film used here is a tin oxide thin film, a thin film composed of a mixture of crystal of tin oxide and indium oxide, or an island-shaped metal film.
Further, in the proposal presented by the present applicant, for a preferable electrical connection of a spacer, on which a film having a high resistance is deposited, to a multi-electron beam source and a face plate, an arrangement is also disclosed for the forming of films at those connection joints. In addition, an arrangement is disclosed wherein, by using conductive frit glass, a spacer on which a film having high resistance and a film having low resistance are deposited is electrically connected to the multi-electron beam source and the face plate, and wherein the spacer is mechanically fixed.
In the display panel of the image display apparatus described above, since a plurality of spacers are arranged in accordance with the display size of the display panel and the thicknesses of the rear plate and the face plate, the number of spacers increases as the display size is enlarged. Accordingly, in the assembly process for the display panel, since the number of procedures required for installing spacers is increased, the manufacturing costs are increased. Further, especially when spacers are elongated, the warping of spacers opposite the rear plate and the face plate is a problem that can not be ignored. That is, when such a warp occurs, great stress is imposed on a spacer that is sandwiched between the rear plate and the face plate, and the spacer may be broken. Therefore, the yield of the spacers during the assembly of the display panel progressively affects the yield of the display panels, and accordingly, manufacturing costs rise.
To form the envelope for the display panel, generally, the face plate, the side wall and the rear plate are sealed by using frit glass. At this time, frit glass is annealed by heating the envelope to approximately 400 to 500xc2x0 C. Because of this heat, a spacer may be expanded relative to the face plate and the rear plate, and be deformed or misaligned.
Further, when a charge prevention film and a film that is used for the preferable electrical connection of the charge prevention film to the electron beam source and the face plate are to be formed on the surface of a spacer, if the spacer is extended in consonance with the size of a display panel, for the films, desired thicknesses and positional accuracy can not be obtained, and desired effects can not be acquired.
Furthermore, when, as is described above, a plurality of types of films are to be formed on the surface of a spacer, the number of film formation procedures is increased, and the films must be formed so that a satisfactory electroconductivity is attained without an oxide film, etc., being formed between the films.
It is a first objective of the present invention to provide an electron beam apparatus, in which spacers are employed, that can be easily assembled, so that the rise in manufacturing costs that accompanies the installation of spacers can be suppressed.
It is a second objective of the present invention to provide an electron beam apparatus that can prevent the destruction of a spacer when it is sandwiched between a rear plate and a face plate.
It is a third objective of the present invention to provide an electron beam apparatus wherein a spacer is prevented from being deformed or misaligned due to the heat used to form a vacuum container for the electron beam apparatus.
It is a fourth objective of the present invention to provide an electron beam apparatus wherein, even with an elongated spacer, a desired film can be formed on the surface of the spacer to prevent charging.
It is a fifth objective of the present invention to obtain electroconductivity even among a plurality of films that are formed on the surface of a spacer and to minimize the increase in the number of procedures.
To achieve the above objectives, an electron beam apparatus according to the present invention is characterized by comprising:
a first substrate that is provided in a vacuum container and that includes a plurality of electron-emitting devices;
a second substrate that in the vacuum container is located opposite the first substrate and that is irradiated by electrons emitted by the electron-emitting devices;
one spacer, at least, that is mounted as an atmospheric-pressure resistant structure on one of the first and the second substrates, that is sandwiched directly between the first and the second substrates, or indirectly via an intermediate member between the first and the second substrates, and that is extended longitudinally in a direction perpendicular to the direction in which the first and the second substrates are positioned opposite each other; and
a support member, for supporting the spacer outside an electron-emitting region that is defined between a region of the first substrate wherein the electron-emitting devices are located, and a region of the second substrate that is irradiated by the electrons,
wherein at least the spacer or the support member has a structure that relieves the stress that is generated when the spacer is sandwiched between the first and the second substrates.
According to the above invention, the interval between the first and the second substrates is maintained by spacers. Since the spacers are self-supported by support members, the positioning of the spacers during the assembly of an electron beam apparatus is easy. Further, since the support members support the spacers outside the electron-emitting region, the space required for the support members need not be taken into account when the electron-emitting devices are to be arranged.
If warping of a spacer occurs, especially if the spacer and a support member are secured to each other, when the spacer is sandwiched between the first and the second substrates, the stress that is generated to straighten the warped spacer is concentrated at that portion whereat the spacer and the support member are secured to each other. But since at the least, either the spacer or the support member is so designed that it can reduce stress, the destruction of the spacer can be prevented. The present invention is particularly effective when the longitudinal length of a spacer is 50 times or greater the interval (the distance between the top end and the bottom end of the spacer) maintained by the spacer. Further, the effects are particularly outstanding when the longitudinal length is 100 times or greater.
Further, an electron beam apparatus according to the present invention is characterized by comprising:
a first substrate that is provided in a vacuum container and that includes a plurality of electron-emitting devices;
a second substrate that in the vacuum container is located opposite the first substrate and that is irradiated by electrons emitted by the electron-emitting devices;
one spacer, at least, that is mounted as an atmospheric-pressure resistant structure on one of the first and the second substrates, that is sandwiched directly between the first and the second substrates, or indirectly via an intermediate member between the first and the second substrates, and that is extended longitudinally in a direction perpendicular to the direction in which the first and the second substrates are positioned opposite each other; and
a support member that, outside an electron-emitting region that is defined between a region of the first substrate wherein the electron-emitting devices are located and a region on the second substrate that is irradiated by the electrons, is mounted on the substrate whereon the spacer is provided so that the support member supports the spacer,
wherein the support member and the spacer are secured to each other, so that a first axis of the support member, which is positioned parallel to the face of the support member that is mounted on the substrate; is substantially parallel to a second axis of the spacer that is extended in the longitudinal direction.
According to the second invention, the support member is mounted on the first or the second substrate and the spacer is fixed to the support member, so that the longitudinal axis is substantially parallel to the mounting face. Therefore, during the assembly of the electron beam apparatus, the stress that is generated at the portion to which the spacer and the support member are fixed can be minimized when the spacer is sandwiched between the first and the second substrates.
Furthermore, an electron beam apparatus according to the present invention is characterized by comprising:
a first substrate that is provided in a vacuum container and that includes a plurality of electron-emitting devices;
a second substrate that in the vacuum container is located opposite the first substrate and that is irradiated by electrons emitted by the electron-emitting devices;
one spacer, at least, that is mounted as an atmospheric-pressure resistant structure on one of the first and the second substrates, that is sandwiched directly between the first and the second substrates, or indirectly via an intermediate member between the first and the second substrates, and that is extended longitudinally in a direction perpendicular to the direction in which the first and the second substrates are positioned opposite each other; and
a support member, for supporting the spacer outside an electron-emitting region that is defined between a region of the first substrate wherein the electron-emitting devices are located, and a region of the second substrate that is irradiated by the electrons,
wherein the spacer has a thermal expansion rate that is smaller than the substrate on which the spacer is mounted.
The electron beam apparatus may heat a vacuum container in order to acquire a vacuum container or to enhance the degree of vacuum provided by the vacuum container. The individual members are thermally expanded by heating. But according to the third invention, since the spacer has a smaller thermal expansion rate than the substrate on which the spacer is mounted, the positional shifting of the spacer, which is caused by the distortion that occurs when the length of the spacer is longer than the substrate, can be prevented.
However, when there is too great a difference between the thermal expansion rates of the substrate and the spacer, the substrate expands too much and a force produced by tension acts on the spacer. Thus, it is preferable that the difference between the thermal expansion rates of the substrate and the spacer be not greater than 5%.
In addition, an electron beam apparatus according to the present invention is characterized by comprising:
a first substrate that is provided in a vacuum container and that includes a plurality of electron-emitting devices;
a second substrate that in the vacuum container is located opposite the first substrate and that is irradiated by electrons emitted by the electron-emitting devices; and
one spacer, at least, that is mounted as an atmospheric-pressure resistant structure on one of the first and the second substrates, that is sandwiched directly between the first and the second substrates, or indirectly via an intermediate member between the first and the second substrates, and that is extended longitudinally in a direction perpendicular to the direction in which the first and the second substrates are positioned opposite each other,
wherein a film, which is to be electrically connected to either the first substrate or the electrode and is not to be charged as easily as the surface of the spacer, is formed on the surface of the spacer at a plurality of portions in the longitudinal direction of the spacer.
According to the fourth invention, on the surface of a spacer a film is formed that is electrically connected either to the electrode that controls the electrons emitted by the electron-emitting devices, or to the first substrate. Therefore, the charging of the surface of the spacer that is accompanied by the emission of electrons is removed. Further, since this film is formed at a plurality of portions in the longitudinal direction of the spacer, the film formation accuracy relative to the position, the shape and the thickness of the film is improved, and a desired film can be obtained.
Moreover, an electron beam apparatus according to the present invention is characterized by comprising:
a first substrate that is provided in a vacuum container and that includes a plurality of electron-emitting devices;
a second substrate that in the vacuum container is located opposite the first substrate and that is irradiated by electrons emitted by the electron-emitting devices; and
one spacer, at least, that is mounted as an atmospheric-pressure resistant structure on one of the first and the second substrates, that is sandwiched directly between the first and the second substrates, or indirectly via an intermediate member between the first and the second substrates, and that is extended longitudinally in a direction perpendicular to the direction in which the first and the second substrates are positioned opposite each other,
wherein on the surface of the spacer are formed a highly resistant film, which is electrically connected either to the first substrate or to the electrode and which is not charged as easily as the surface of the spacer, and a low resistant film, which is laminated over or under the highly resistant film in the electrically connected region and which has a sheet resistance smaller than the highly resistant film, and
wherein the highly resistant film and the low resistant film contain the same metal elements but have different compositions.
According to the fifth invention, the highly resistant film and the low resistant film are deposited on the surface of a spacer. The charging of the spacer surface is removed by the highly resistant film, while the electric connection of the highly resistant film and the first substrate or the electrode is satisfactorily effected by the low resistant film, and the trajectory of electrons that are emitted by the electron-emitting device near the spacer is controlled. Since the highly resistant film and the low resistant film contain the same elements but have different compositions, a satisfactory continuity is maintained at the boundary between the low resistant film and the highly resistant film, and a desired low resistant film and a desired highly resistant film can be sequentially formed by using the same film formation device. Especially when these films are to be deposited by the vapor-phase film deposition method, the films can be deposited in the same chamber without the vacuum atmosphere being adversely affected. Thus, an unwanted oxide film is not formed at the lamination of the low resistant film and the highly resistant film.